Cryogels are solid elastomers containing over 80% water which are produced when solutions of higher molecular weight poly(vinyl alcohol) (PVA) of high degree of hydrolysis are subjected to repeated freeze-thaw cycles. Such cryogels are tough, slippery, elastomeric, resilient, insoluble in water below 50.degree. C., and nontoxic.
The fact that cryogels may be produced without the use of cross-linking agents or other adjuvants is a desirable feature emphasized in a review of the scientific literature on such gels (N. A. Peppas and S. R. Stauffer. Reinforced uncrosslinked poly(vinyl alcohol) gels produced by cyclic freezing-thawing processes: a short review. Journal of Controlled Release, 16, 305-310, 1991).
Transdermal films of PVA containing drugs such as corticosteroids, inflammation inhibitors, sedatives, tranquilizers, antihypertensives, diuretics, antibiotics, anesthetics, and vitamins have been disclosed (M. Sunamiu, et al, Transdermal films for drug preparations. Chemical Abstracts 112:240485m, 1990). These films used PVA of 500-2400 degree of polymerization (molecular weight of about 22,000-105,000 daltons) and were used to administer pharmaceuticals through the skin.
The anti-inflammatory indomethacin has been incorporated into cryogels. Its release was found to be in direct proportion to the square of time. PVA cryogels cross-linked with glutaraldehyde were shown to release indomethacin with zero order kinetics (A. Takamura, M. Arai, F. Ishii. Drug release from freeze-thaw poly(vinyl alcohol) gel. Yakugaku Zasshi, 107, 233-237, 1987).
PVA hydrogels have been used as rectal suppositories for controlled release for beta-blockers. Straight line release of the drugs superior to that of other suppositories was observed (K. Morimoto, S. Fukanoki, K. Morisaka, S. Hyon and Y. Ikada. Design of a poly(vinyl alcohol) hydrogel as a controlled-release vehicle for rectal administration of dl-propranolol hydrochloride and atenolol. Chem. Pharm. Bull. 37, 2491-2495, 1989).
The inclusion of phospholipids in the PVA hydrogels was shown to slow the release of propranolol (K. Morimoto, S. Fukanoki, Y. Hatakeyama, A. Nagayasu, K. Morisaka, S. Hyon. Design of a poly(vinyl alcohol) hydrogen containing phospholipid as controlled-release vehicle for rectal administration of (+/-)-propranolol hydrochloride. J. Pharm. Pharmacol, 42, 720-722, 1990).
Hydrogels containing indomethacin, however, were inferior to conventional suppositories in their effect on dog plasma levels (K. Morimoto, A. Nagayasu, S. Fukanoki, K. Morisaka, S. Hyon and Y. Ikada. Evaluation of poly(vinyl alcohol) hydrogels as a sustained-release vehicle for rectal administration of indomethacin. Pharm. Research, 6, 338-341, 1989).
PVA hydrogels containing bunitrolol-HCl gave straight line release as the square of time over 60% of the total release time (K. Morimoto, A. Nagayasu, S. Fukanoki, K. Morisaka, S. Hyon and Y. Ikada. Evaluation of poly(vinyl alcohol) hydrogel as sustained-release vehicle for transdermal system of bunitrolol-HCl. Drug Devel. Ind. Phar., 16, 13-29, 1990).
The manufacture of a poultice or topical patch for transdermal delivery by wrapping a film which may contain a polyhydric alcohol, starch, hyaluronic acid or propylene glycol alginate with a PVA sheet has been disclosed (M. Shigemitsu, Jpn KTK 01 16,718, Jan. 20, 1989).
The use of PVA hydrogel as a soft contact lens material has been reported (M. Kita, Y. Ogura, Y. Honda, S. Hyon, W. Cha and Y. Ikada. Evaluation of polyvinyl alcohol hydrogel as a soft contact lens material. Graefe's Arch. Clin. Exp. Ophthal. 228, 533-537, 1990).
Controlled-release systems for oral administration of therapeutic agents are described in U.S. Pat. No. 4,221,778 to Raghunathan, issued Sep. 9, 1980 in which a preparation of a drug resin complex is coated with an impregnating agent in order to provide the desired controlled release of the drug.
Controlled-release systems for oral administration of therapeutic agents are described in U.S. Pat. No. 4,847,077 to Raghunathan, issued Jul. 11, 1989 in which a preparation of a drug resin complex is coated with glycerin and then coated with a water-permeable diffusion barrier in order to provide the desired controlled release of the drug.
Controlled-release systems for oral administration of therapeutic agents are described in U.S. Pat. No. 4,967,047 to Kelleher et al, issued Feb. 26, 1991 in which a preparation of a drug resin complex having a drug content above 38% by weight is coated with a water-permeable diffusion barrier.
Although these poly(vinyl alcohol) cryogel materials have been used to accomplish transdermal delivery, the prior art has not disclosed compositions of poly(vinyl alcohol) and methods of their preparation for bandages which effectively release therapeutic agents directly to a wound, trauma or surgical site. The use of ion exchange resins incapsulated in various coatings for oral administration of therapeutic agents has been described, however, the prior art has not disclosed the use of ion exchange resins incapsulated in poly(vinyl alcohol) cryogels for use in bandages which effectively release therapeutic agents directly to a wound, trauma or surgical site. The prior art has also not disclosed the use of ion exchange-drug complexes enclosed in poly(vinyl alcohol) cryogels for the transdermal delivery of therapeutic agents or for use in oral pharmaceutical preparations for administration of drugs in the gastrointestinal tract.